In article <mt2dnVtxyYjognbbnZ2dnUVZ_hudnZ2d@web-ster.com>, 
tim@seemywebsite.com says...
> On Fri, 14 Sep 2007 20:57:52 +0000, AmyLe wrote:
> 
> > Hey,
> > 
> > Oh yeah, I'm using the ADC78H90 (http://www.national.com/pf/DC/
> > ADC78H90.html).  But in general, where should I start?
> 
> I general, you should start with three things: the ADC data sheet, the
> processor data sheet, and a brain.  By preference the brain should belong
> to you, but if you must use one that doesn't then you should consider
> brain training aids, like offers of beer.
> 
> Aside from these three necessary things, an oscilloscope is handy, to let
> the brain make sure that the code is doing what it should.
> 
> Have the brain read both of the data sheets, particularly the sections
> that pertain to the SPI interface.  Have the brain write whatever code is
> necessary to make the processor emit the necessary bit stream for the ADC,
> and read in the bit stream from the ADC.  While you're at it, have the
> brain look at the schematic of the board.
> 
> This may not work at first -- you may have to flog the brain for a while
> to get it to write code that works.  Hence the preference for using your
> own brains -- other people tend to get upset when you flog their brains. 
> This is also where the 'scope comes in handy -- usually having a 'scope
> handy during the initial trials will significantly reduce the amount of
> time you have to flog the brain.
> 
> Good luck, and don't forget the beer.
> 

Simplified versin:  Make sure that you can see a clock on SCLK when you
call the ADC conversion routine.  No Clock to ADC == No data!

You can do this stuff without fancy logic analyzers.  You can do it 
without a COMPLETE understanding of the chip.  You CANNOT do it without
an oscilloscope!

Mark Borgerson

AmyLe wrote:
> Hey,
> 
> Oh yeah, I'm using the ADC78H90 (http://www.national.com/pf/DC/
> ADC78H90.html).  But in general, where should I start?
> 
1) figure the correct SPI.
The data may transfer on the rising or falling edge of the clock.
Check the MPU data sheet and the A2D data sheet timing diagrams.
2) Check the clock rate.  the A2D has a maximum clock rate and sometimes 
a minimum rate.

On Fri, 14 Sep 2007 20:57:52 +0000, AmyLe wrote:

> Hey,
> 
> Oh yeah, I'm using the ADC78H90 (http://www.national.com/pf/DC/
> ADC78H90.html).  But in general, where should I start?

I general, you should start with three things: the ADC data sheet, the
processor data sheet, and a brain.  By preference the brain should belong
to you, but if you must use one that doesn't then you should consider
brain training aids, like offers of beer.

Aside from these three necessary things, an oscilloscope is handy, to let
the brain make sure that the code is doing what it should.

Have the brain read both of the data sheets, particularly the sections
that pertain to the SPI interface.  Have the brain write whatever code is
necessary to make the processor emit the necessary bit stream for the ADC,
and read in the bit stream from the ADC.  While you're at it, have the
brain look at the schematic of the board.

This may not work at first -- you may have to flog the brain for a while
to get it to write code that works.  Hence the preference for using your
own brains -- other people tend to get upset when you flog their brains. 
This is also where the 'scope comes in handy -- usually having a 'scope
handy during the initial trials will significantly reduce the amount of
time you have to flog the brain.

Good luck, and don't forget the beer.

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

AmyLe wrote:
> 
> Oh yeah, I'm using the ADC78H90 (http://www.national.com/pf/DC/
> ADC78H90.html).  But in general, where should I start?

Start what?  Believe it or not, that is why normal Usenet users
quote the pertinant parts of the previous messages.  Usenet is a
'best efforts' delivery mechanism, and there is no guarantee that
your reader has ever, or ever will in the future, read any other
messages.  Thus it is essential that the quotes make each message
complete in itself.

-- 
 Chuck F (cbfalconer at maineline dot net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>

-- 
Posted via a free Usenet account from http://www.teranews.com

Hey,

Oh yeah, I'm using the ADC78H90 (http://www.national.com/pf/DC/
ADC78H90.html).  But in general, where should I start?

"AmyLe" <amyle.01@gmail.com> wrote in message 
news:1189789319.398691.36650@k79g2000hse.googlegroups.com...
> I want to know how I can interface the SPI with an external ADC.  Has
> anyone done this before? Also, I prefer using polling instead of
> interrups.

First, you need to select an ADC.  No additional work can proceed until 
you've selected it.

JJS

Hi,

I want to know how I can interface the SPI with an external ADC.  Has
anyone done this before? Also, I prefer using polling instead of
interrups.



Here is my INIT SPI function:

=============================INIT_SPI=================================

void Init_SPI(void)
{
  P3SEL |= 0x3F;		      // Select P3.0,1,2,3,4,5
  P3DIR |= 0x0B;                    // Select P3.1,3 as output
directions
  P3OUT &= ~0x01;
  ME1 |= USPIE0;                    // ENABLE USART0 SPI
  UCTL0 |= CHAR + SYNC + MM;        //  8-bit data, SPI mode
  UTCTL0 |=  CKPH + CKPL + SSEL1;  //  Inv.delay, ACLK
  UBR00 = 0x2A;                     // Baud Rate = 115200
  UBR10 = 0x0;
  UMCTL0 = 0x0;                     // Clear Modulation
  UCTL0 &= ~SWRST;                  // Initialize USART state machine

  //_BIS_SR(LPM3_bits + GIE);         // Enter LPM0 w/interrupt

} //end Init_SPI

====================================================================

I'm using IAR.  Thank you so much for your help!